Unknown Problem

[Brudd]

Hi, Looking for some help,
I have a 01 grand cherokee laredo, 4.0 auto, 81,*** miles. The fuel pump is good & I don't think the pcm is the issue.

I drive it around the block then let it sit idling for 15 minutes, it starts to sputter, the gas pedal has very little effect and when it is used I get a few pops and it stalls. 30-40 minutes later it will start again. If I am on the road, it just plain stalls, again, 30-40 minutes later it will start again.

The engine light isn't on and its not reading any codes.

Any ideas? Suggestions? Crank sensor? Cam sensor? I don't want to randomly replace things until I stumble across the problem.

Thanks

 

[JPNinPA]

Check that you are not overheating.
Even though the fuel pump is good what is your fuel pressure?

Plugs and wires good?


JPNinPA
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[Brudd]

Not overheating, New fuel pump (don't know the pressure), new wires.

When it is running/driving, goes like a bat-out-of-hell, for about 15 minutes or so.

 

[JPNinPA]

Is there water in your oil? Or oil in your water?

To check you could check under the oil filler cap. Check the dip stick or change the oil and see if it looks like milkshake.

You could also do a compression test.


JPNinPA
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[Brudd]

There's no oil in the water, no water in the oil.

 

[JPNinPA]

With no water/oil issue, so, it's not a cracked head or leaky head gasket.
Again I'd start by checking your fuel pressure despite it being new. New does not always mean good.
BTW was this an issue before changing the fuel pump?

By 15 min you should be normal operating temp. 195-210 deg.
I'd check the temp sensor that goes to the pcm and the O2sensors.

What rpm do you idle at?

Popping should throw a code?


JPNinPA
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[Brudd]

I bought the jeep with the problem. The previous owner had the problem before he swapped out the fuel pump.
Just found a broken wire (green with an orange stripe) that goes from the injectors to beneath the master cylinder, I re-connected it. I'll see what happens tomorrow.
It is at operating temps for a few minutes before it stalls.
Idles at normal rpm.

 

[jeepgirlsrock]

Fuel filter, it has two jobs. It not only filters your fuel but it also regulates your pressure. I bought my jeep with the same problem. I knew it had to be a fuel delivery issue so I started with the cheapest part to replace, I got lucky , itwas the problem.


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[Dragon5126]

there is a seperate fuel regulator mounted to the fuel pump/fuel filter assembly some parts houses sell it as part of a filter unit, others sell it as a seperate piece, but it is NOT the filter. On this particular vehicle the regulator is external As shown by this link.
2001 JEEP GRAND CHEROKEE 4.0L L6 Fuel Injection Pressure Regulator | RockAuto

 

[Dragon5126]

what is described is ALWAYS a fuel delivery issue, However with computer controlled (pcm/ecu) vehicles there are numerous issues that can cause issues that shut the fuel pump or injectors down, check for hard and soft codes and deal with them as needed. You could have a heat related intermittent power connection for all you know as the idiots who designed these vehicles put the power distribution box right over the exhaust... The point I'm making is dont say "it isnt" until you find the "It Is" take the O2 sensor for a prime example, replace the cat back exhaust with a free flow system and go crazy trying to fix the O2 errors, replacing sensor after sensor util someoe keys you into using an NTK sensor and like magic the problem is fixed, even though all the other sensors you tried were perfectly good. I had that issue on my 06 TJ, I even made an adaptor to limit te amunt of exhaust gas the O2 sensor got, that worled for 6 months and then the codes came back. Then a custom shop out west told me about the NTK sensors, NOT NGK, they must be NTK... even though they are both Nippondenso. these issues are PIFM pure effing magic, I swear.